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Astronomers have glimpsed a 'protocluster' of galaxies as they
appeared only a billion years after the Big Bang, making it the
most distant galaxy cluster yet seen, a report in today's issue
of the journal Nature announced.

Using a slew of telescopes, including NASA's Spitzer, Chandra and
Hubble space observatories, and the Keck telescope in Hawaii,
Peter Capak of California Institute of Technology and his team
were able to locate the beginnings of a cluster of galaxies from
very early in the universe.

A
galaxy cluster is a grouping of hundreds of individual
galaxies bound together by gravity. A typical cluster contains
between 50 and 1000 galaxies, with a mass ranging from 100
trillion to 1 quadrillion times the mass of the sun. The Milky
Way is part of a galaxy cluster known as the Virgo Cluster, which
contains roughly 2,000 galaxies.

But finding and studying the birthplace of these regions is
difficult. Early protoclusters are rare, and challenging to
locate. Astronomers must look very far away, so that they are
viewing objects whose light has taken billions of years to travel
to Earth, thus presenting them with a window back in
time.

"In an area 16 times the size of the full moon, we can expect to
find only two to five protoclusters," Capak told SPACE.com

To hunt down protoclusters, Capak and his colleagues searched for
brighter, easier-to-find objects such as quasars, starbursts, and
massive galaxies — all of which could indicate the presence of a
young galaxy cluster. They searched in the same area of the sky
studied by the Cosmic Evolution Survey (COSMOS).

Within the field, they found a galaxy called AzTEC-3 that was
forming stars at a rapid pace, and a quasar – a bright outpouring
of light that occurs when mass falls into a black hole.

Like all
starburst galaxies, AzTEC-3 has an exceptionally high rate of
star formation. Massive stars are created from the abundant gas
within the galaxy, burning quickly and brightly, and often
exploding as supernovas. This makes starburst galaxies among the
brightest galaxies around.

Also in close range lies a
quasar, a compact region in a massive galaxy powered by its
supermassive black hole. Formed around black hole accretion
disks, quasars can outshine the galaxy they inhabit, and are the
most luminous objects in the universe.

Because of their high luminosity, starbursts and quasars are
relatively easy to locate in the night sky. In order to function,
both require space dense with gas and other materials. They tend
not to exist in isolation, but rather in heavily populated areas.

"These types of regions are associated with clusters and
protoclusters," Capak told said. "Around this system, we found
eleven times more galaxies than you would expect in a random area
of the sky."

The dense galactic population indicated the presence of a
protocluster. More than 40 million light-years across, this
protocluster lies nearly 13 billion light-years away from Earth.

Because of the time it took this object's light to travel to us,
astronomers saw it as it was only a billion years after the Big
Bang.

Studying the environment around the protocluster helps
astronomers understand what led to its creation. Similarly, the
interactions within the protocluster reveal a great deal about
cluster formation at the beginning of the universe.

"What's particularly interesting about this one is that we can
characterize what's going on," Capak said. "We can get an idea of
what the conditions were in early protoclusters."